Public Class Form1
    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click ///当按钮1被按下时开始
        If 
        
       (TextBox1.Text = "") 
       (TextBox2.Text = "")
        Then   ///信息框内容等于空的情况开始

            MessageBox.Show("NO", "TEST")   ///弹出NO
        End If                         ///信息框内容等于空的结束

        If (TextBox1.Text = "1234") Then  ///信息框内容等于1234的情况开始
            MessageBox.Show("yes", "TEST")///弹出YES
        End If                            ///信息框内容等于1234的情况结束
    End Sub                          ///当按钮1被按下时结束
End Class